Fire alarm systems are often installed within commercial, residential, or governmental buildings, for instance. Examples of these buildings include hospitals, warehouses, schools, hotels, shopping malls, office buildings, and casinos. The fire alarm systems monitor for the existence of fire conditions, such as smoke or heat, and alert occupants when the fire conditions are detected.
Fire alarm systems include fire alarm system devices such as notification appliance devices for alerting occupants of a potential fire. Notification appliance devices include notification units that generate alert signals (e.g., audible signals or visible signals) for indicating an alarm (i.e., potential fire) to occupants.
Other fire alarm system devices include initiation devices that can detect fire conditions or be manually activated. One type of initiation device is a detector device that includes a sensor unit for detecting the existence of fire conditions (i.e., smoke or heat). Another type of initiation device is a notification/detector combination device that includes a notification unit and a smoke/heat sensor unit. Still another type of initiation device is a manually activated unit such as a fire alarm box/pull station.
System controllers of the fire alarm systems monitor the initiation devices and activate the notification appliance devices. For example, when fire conditions (i.e., smoke or heat) are detected by the initiation devices (e.g., detector devices and notification/detector combination devices), the initiation devices send alarm signals to the system controller. The system controller responds to the alarm signals by activating the notification appliance devices to generate the alert signals to indicate an alarm (i.e., alert occupants of potential fire).
The system controller communicates with the initiation devices and the notification appliance devices via wired and/or wireless networks. For example, in wired fire alarm systems, several initiation devices and notification appliance devices are wired to a common pair of system lines from the system controller. The system controller then communicates with the devices via the system lines. In wireless fire alarm systems, the system controller communicates wirelessly with the devices possibly via a wireless access point.
For wired fire alarm systems, the system controller usually provides power to the initiation devices and notification appliance devices via the system lines. Typically, the system controller has a power source such as a DC power unit to supply power on the system lines. This DC power unit supplies power at a fixed voltage and typically is current limited to providing a maximum current.
For wireless fire alarm systems, the initiation devices and notification appliance devices will typically be battery powered using either primary batteries or primary and secondary batteries. The primary batteries are typically used to power the low power components of the system. Alternatively, the secondary batteries typically provide power on an intermittent basis to notification units, for example, that are relatively high power components.